Heat exchanger and hot water apparatus

ABSTRACT

A latent heat recovery heat exchanger includes a heat exchange portion and a case. The heat exchange portion includes a plurality of heat transfer plates layered on one another. The case accommodates the plurality of heat transfer plates of the heat exchange portion. The heat exchange portion includes a front plate portion provided as an outermost layer of the heat exchange portion. The front plate portion of the heat exchange portion forms a part of the case.

TECHNICAL FIELD

The present invention relates to a heat exchanger and a hot water apparatus.

BACKGROUND ART

A heat exchanger in which a plurality of heat transfer plates are accommodated in a case is disclosed, for example, in WO2015/141995 (PTL 1).

In the heat exchanger in the literature above, the plurality of heat transfer plates are sandwiched from the front and the rear between a front member and a rear member of a case divided into two parts. The front member and the rear member of the case are fixed to each other by a screw at a boundary between the front member and the rear member of the case divided into two parts.

CITATION LIST Patent Literature

PTL 1: WO2015/141995

SUMMARY OF INVENTION Technical Problem

In the heat exchanger in the literature above, members which form the plurality of heat transfer plates and a member which forms the case are required. Therefore, the number of members disadvantageously increases.

The present invention was made in view of the problem above, and an object thereof is to provide a heat exchanger capable of achieving a reduced number of members and a hot water apparatus including the same.

Solution to Problem

A heat exchanger according to the present invention includes a heat exchange portion and a case. The heat exchange portion includes a plurality of heat transfer plates layered on one another. The case accommodates the plurality of heat transfer plates of the heat exchange portion. The heat exchange portion includes a front plate portion provided as an outermost layer of the heat exchange portion. The front plate portion of the heat exchange portion forms a part of the case.

According to the heat exchanger in the present invention, the front plate portion of the heat exchange portion forms a part of the case. Therefore, the front plate portion of the heat exchange portion can serve also as the case. Therefore, the number of members can be reduced.

The heat exchanger further includes a pipe joint portion attached to the front plate portion, the pipe joint portion being configured to allow water and/or hot water to flow in and out of the plurality of heat transfer plates. Since the pipe joint portion is attached to the front plate portion, no sealing member such as a gasket is required for sealing a gap between the pipe joint portion and the front plate portion. Since no sealing member such as a gasket is required for sealing a gap between the pipe joint portion and the front plate portion, there is no possibility of leakage of heating gas (combustion gas) through the gap between the pipe joint portion and the front plate portion to the outside of the heat exchanger due to poor sealing. Therefore, sealability can be improved.

In the heat exchanger, the case includes a rear wall portion arranged to sandwich the plurality of heat transfer plates between the rear wall portion and the front plate portion and a pair of sidewall portions which extends from opposing ends of the rear wall portion toward the front plate portion. The pair of sidewall portions is joined to the front plate portion. Therefore, no sealing member such as a gasket is required for sealing a gap between the front plate portion and the pair of sidewall portions. Since no sealing member such as a gasket is required for sealing a gap between the front plate portion and the pair of sidewall portions, there is no possibility of leakage of heating gas (combustion gas) through the gap between the front plate portion and the pair of sidewall portions to the outside of the latent heat recovery heat exchanger due to poor sealing. Since no sealing member such as a gasket is required for sealing a gap between the front plate portion and the pair of sidewall portions, no operation for attaching the sealing member is required. Therefore, assembly of the latent heat recovery heat exchanger is facilitated.

The heat exchanger further includes a flange member arranged at an upper end portion of the case. The flange member includes an extension portion which extends from the upper end portion to the outside of the case and an opening provided on an inner side of the extension portion. The extension portion is provided to surround the opening. Therefore, the sealing member can be placed on the extension portion to surround the opening. Sealing as surrounding the opening can thus be achieved.

In the heat exchanger, the flange member includes a rising coupling portion which rises upward from the extension portion along the opening. The upper end portion of the case is inserted in the opening. The rising coupling portion is joined from an outer side to the upper end portion of the case inserted in the opening. Therefore, the rising coupling portion can readily be welded to the upper end portion of the case.

In the heat exchanger, the rising coupling portion includes a peripheral wall portion which surrounds the opening and a first cut portion provided in an upper edge of the peripheral wall portion. The case includes a second cut portion provided in an upper edge of the upper end portion thereof. The first cut portion is arranged to be superimposed on the second cut portion. Therefore, drainage water can flow to the opening through the first cut portion and the second cut portion. Drainage water can thus readily be discharged.

In the heat exchanger, the opening is quadrangular when the flange member is viewed from above. The first cut portion and the second cut portion are provided in each of four corners of the opening. Therefore, the first cut portion can be made by cutting and erecting four corners of the opening in the flange member. Therefore, the first cut portion can readily be made.

A hot water apparatus according to the present invention includes a combustion apparatus which generates heating gas, a sensible heat recovery heat exchanger which recovers sensible heat of heating gas generated by the combustion apparatus, and the heat exchanger described above as a latent heat recovery heat exchanger which recovers latent heat of heating gas. According to the hot water apparatus in the present invention, a hot water apparatus which can achieve a reduced number of members of the heat exchanger can be provided.

A hot water apparatus according to the present invention includes a combustion apparatus which generates heating gas, a sensible heat recovery heat exchanger which recovers sensible heat of heating gas generated by the combustion apparatus, and the heat exchanger described above as a latent heat recovery heat exchanger which recovers latent heat of heating gas. The sensible heat recovery heat exchanger includes a heat transfer tube for flow of water and/or hot water. The heat transfer tube includes a water entry portion for entry of water and/or hot water thereinto. Any one of the first cut portion and the second cut portion provided in each of four corners of the opening is arranged directly under the water entry portion. According to the hot water apparatus in the present invention, the first cut portion and the second cut portion can be arranged directly under the water entry portion where drainage water is likely.

Therefore, drainage water can efficiently be discharged.

Advantageous Effects of Invention

As described above, according to the present invention, a heat exchanger which can achieve a reduced number of members and a hot water apparatus including the same can be provided.

BRIEF DESCRIPTION OF DRAWINGS

FIG. 1 is a diagram schematically showing a construction of a hot water apparatus in one embodiment of the present invention.

FIG. 2 is a perspective view schematically showing a construction of a sensible heat recovery heat exchanger and a latent heat recovery heat exchanger in one embodiment of the present invention.

FIG. 3 is an exploded perspective view schematically showing the construction of the sensible heat recovery heat exchanger and the latent heat recovery heat exchanger in one embodiment of the present invention.

FIG. 4 is a perspective view schematically showing the construction of the latent heat recovery heat exchanger in one embodiment of the present invention.

FIG. 5 is an exploded perspective view schematically showing the construction of the latent heat recovery heat exchanger in one embodiment of the present invention.

FIG. 6 is an exploded perspective view schematically showing a construction of a heat exchange portion of the latent heat recovery heat exchanger in one embodiment of the present invention.

FIG. 7 is an enlarged view showing a VII portion in FIG. 4.

FIG. 8 is a cross-sectional view showing a flow of drainage water in the sensible heat recovery heat exchanger and the latent heat recovery heat exchanger in one embodiment of the present invention.

FIG. 9 is a cross-sectional view showing a flow of drainage water in the latent heat recovery heat exchanger in one embodiment of the present invention.

FIG. 10 is a perspective view schematically showing a construction of the latent heat recovery heat exchanger in Comparative Example 1.

FIG. 11 is an exploded perspective view schematically showing the construction of the latent heat recovery heat exchanger in Comparative Example 1.

FIG. 12 is a perspective view showing a portion corresponding to FIG. 7 in Comparative Example 2.

FIG. 13 is a cross-sectional view showing a flow of drainage water in the latent heat recovery heat exchanger corresponding to FIG. 9 in Comparative Example 2.

FIG. 14 is a perspective view showing the portion corresponding to FIG. 7 in a modification of one embodiment of the present invention.

DESCRIPTION OF EMBODIMENTS

An embodiment of the present invention will be described below with reference to the drawings.

A construction of a hot water apparatus in one embodiment of the present invention will initially be described.

Referring to FIG. 1, a hot water apparatus 100 in the present embodiment mainly includes a latent heat recovery heat exchanger (secondary heat exchanger) 10, a sensible heat recovery heat exchanger (primary heat exchanger) 20, a combustion apparatus (burner) 30, a chamber 31, a fan assembly 32, a duct 33, a venturi 34, an orifice 35, a gas valve 36, a pipe 40, a bypass pipe 41, a three-way valve 42, a liquid to liquid heat exchanger 43, a hydronic pipe 44, and a housing 50. All of components except for housing 50 among the components above are accommodated in housing 50.

Fan assembly 32 is configured to send mixture gas of fuel gas and air taken in from the outside of housing 50 to combustion apparatus 30. Fan assembly 32 includes a fan case, an impeller arranged in the fan case, and a drive source (such as a motor) for rotating the impeller.

Fuel gas flows to venturi 34 through gas valve 36 and orifice 35. Gas valve 36 is configured to control a flow rate of fuel gas. Air taken in from the outside of housing 50 flows to venturi 34.

Fuel gas and air are mixed in venturi 34. Venturi 34 is configured to increase a flow velocity of mixture gas by reducing the flow of mixture gas of fuel gas and air.

Mixture gas which has passed through venturi 34 is sent by fan assembly 32 to combustion apparatus 30 through chamber 31.

Combustion apparatus 30 is configured to generate heating gas (combustion gas). Combustion apparatus 30 is configured to supply combustion gas to sensible heat recovery heat exchanger 20 and latent heat recovery heat exchanger 10.

Combustion apparatus 30 is an inverse combustion type apparatus which supplies combustion gas downward. Mixture gas issued from combustion apparatus 30 is ignited by an igniter 30 a and becomes combustion gas.

Combustion gas sequentially passes through sensible heat recovery heat exchanger 20 and latent heat recovery heat exchanger 10. Thereafter, combustion gas is discharged to the outside of housing 50 through duct 33. Therefore, combustion gas flows downward from above through the inside of sensible heat recovery heat exchanger 20 and latent heat recovery heat exchanger 10, changes its direction in duct 33, and flows upward from below.

Each of sensible heat recovery heat exchanger 20 and latent heat recovery heat exchanger 10 is configured to exchange heat with combustion gas supplied by combustion apparatus 30. Sensible heat recovery heat exchanger 20 is attached under combustion apparatus 30 and latent heat recovery heat exchanger 10 is attached under sensible heat recovery heat exchanger 20.

Sensible heat recovery heat exchanger 20 is a heat exchanger for recovering sensible heat of combustion gas. Sensible heat recovery heat exchanger 20 recovers sensible heat of heating gas (combustion gas) generated by combustion apparatus 30. Latent heat recovery heat exchanger 10 is a heat exchanger for recovering latent heat of combustion gas. Latent heat recovery heat exchanger 10 recovers latent heat of heating gas (combustion gas). Water vapor of combustion gas is condensed in latent heat recovery heat exchanger 10 and condensed water (drainage water) is produced. Drainage water is drained to the outside of housing 50 through a part of duct 33.

When a temperature of incoming water and/or hot water is low also in sensible heat recovery heat exchanger 20 or when an amount of heating by combustion apparatus 30 is small, drainage water is produced also in sensible heat recovery heat exchanger 20. Drainage water is drained to the outside of housing 50 through a part of duct 33 via latent heat recovery heat exchanger 10.

Sensible heat recovery heat exchanger 20 and latent heat recovery heat exchanger 10 are connected to each other through pipe 40. A part of pipe 40 on a water entry side relative to latent heat recovery heat exchanger 10 and a part of pipe 40 on a hot water exit side relative to sensible heat recovery heat exchanger 20 are bypassed by bypass pipe 41.

The part of pipe 40 on the hot water exit side relative to sensible heat recovery heat exchanger 20 and bypass pipe 41 are connected to each other by three-way valve 42. Three-way valve 42 is constructed to be able to switch between a flow path from sensible heat recovery heat exchanger 20 to a hot water outlet of pipe 40 and a flow path from sensible heat recovery heat exchanger 20 to bypass pipe 41.

Liquid to liquid heat exchanger 43 is connected to bypass pipe 41. Hydronic pipe 44 connected to a hydronic terminal is inserted in liquid to liquid heat exchanger 43. Warm water warmed as a result of passage through sensible heat recovery heat exchanger 20 and latent heat recovery heat exchanger 10 flows in liquid to liquid heat exchanger 43. As warm water which flows in liquid to liquid heat exchanger 43 flows outside hydronic pipe 44, heat can be exchanged between warm water which flows in liquid to liquid heat exchanger 43 and warm water which flows in hydronic pipe 44.

Water supplied to hot water apparatus 100 becomes hot as a result of heat exchange with combustion gas in sensible heat recovery heat exchanger 20 and latent heat recovery heat exchanger 10. Hot water can thus be supplied by hot water apparatus 100.

Warm water which returns from the hydronic terminal passes through hydronic pipe 44 to be warmed as a result of heat exchange with warm water warmed by sensible heat recovery heat exchanger 20 and latent heat recovery heat exchanger 10 in liquid to liquid heat exchanger 43 and thereafter it is supplied again to the hydronic terminal. Warm water can thus be supplied to the hydronic terminal by hot water apparatus 100.

A plate type heat exchanger in the present embodiment is applied to latent heat recovery heat exchanger 10 of hot water apparatus 100.

A construction of a heat exchanger set in the present embodiment will now be described with reference to FIGS. 2 and 3. The heat exchanger set includes latent heat recovery heat exchanger 10, sensible heat recovery heat exchanger 20, and a sealing member 60. Sensible heat recovery heat exchanger 20 is arranged on latent heat recovery heat exchanger 10 with sealing member 60 being interposed. Sealing member 60 lies between latent heat recovery heat exchanger 10 and sensible heat recovery heat exchanger 20. Sealing member 60 is in a surrounding shape. Sealing member 60 is in a form of a flat plate.

Sensible heat recovery heat exchanger (primary heat exchanger) 20 mainly includes a case 21, a header 22, and a heat transfer tube 23. Case 21 includes a first sidewall 21 a to a fourth sidewall 21 d. First sidewall 21 a to fourth sidewall 21 d are connected in the order of first sidewall 21 a to fourth sidewall 21 d. Case 21 forms a frame which opens upward and downward. Combustion gas is fed through the upper opening and combustion gas is exhausted through the lower opening. First sidewall 21 a and third sidewall 21 c face each other and second sidewall 21 b and fourth sidewall 21 d face each other.

Header 22 is provided on an outer surface of first sidewall 21 a. A pipe joint 24 a on the water entry side and a pipe joint 24 b on the hot water exit side are attached to header 22 provided on the outer surface of first sidewall 21 a. Not-shown header 22 is provided also on an outer surface of third sidewall 21 c.

Header 22 provided on the outer surface of first sidewall 21 a and header 22 provided on the outer surface of third sidewall 21 c are connected to each other through a plurality of heat transfer tubes 23. The plurality of heat transfer tubes 23 are provided in a region surrounded by first sidewall 21 a to fourth sidewall 21 d as well as in second sidewall 21 b and fourth sidewall 21 d. Heat transfer tube 23 has a water entry portion for entry of water and/or hot water in heat transfer tube 23. The water entry portion is a portion where water and/or hot water enters heat transfer tube 23 first.

Water and/or hot water introduced from pipe joint 24 a on the water entry side reaches header 22 provided on the outer surface of third sidewall 21 c through not-shown heat transfer tube 23 from header 22 provided on the outer surface of first sidewall 21 a. Water and/or hot water which has reached header 22 provided on the outer surface of third sidewall 21 c reaches header 22 provided on the outer surface of first sidewall 21 a through an adjacent heat transfer tube 23 connected to header 22. Water and/or hot water which has reached header 22 provided on the outer surface of first sidewall 21 a reaches header 22 provided on the outer surface of third sidewall 21 c through an adjacent heat transfer tube 23 connected to the header.

Water and/or hot water further goes back and forth between header 22 provided on the outer surface of first sidewall 21 a and header 22 provided on the outer surface of second sidewall 21 b through heat transfer tube 23. Finally, water and/or hot water exits from pipe joint 24 b on the hot water exit side. Thus, water and/or hot water which flows in from pipe joint 24 a on the water entry side flows out of pipe joint 24 b on the hot water exit side through header 22 provided on the outer surface of first sidewall 21 a, heat transfer tube 23, and header 22 provided on the outer surface of third sidewall 21 c.

Referring to FIGS. 2 and 3, latent heat recovery heat exchanger (secondary heat exchanger) 10 mainly includes a heat exchange portion 11, a case 12, a flange member 13, and a pipe joint portion 14. Case 21 of sensible heat recovery heat exchanger 20 is greater in width dimension than case 12 of latent heat recovery heat exchanger 10.

Referring to FIGS. 3 to 5, heat exchange portion 11 includes a front plate portion 11 a, a plurality of heat transfer plates 11 b, and a rear plate portion 11 c. Front plate portion 11 a and rear plate portion 11 c are arranged to sandwich the plurality of heat transfer plates 11 b therebetween.

Front plate portion 11 a is provided as an outermost layer of heat exchange portion 11. Front plate portion 11 a is brazed to a front surface of heat transfer plate 11 b arranged in the forefront among the plurality of heat transfer plates 11 b. Front plate portion 11 a is greater in thickness than heat transfer plate 11 b. Front plate portion 11 a can thus reinforce heat transfer plate 11 b.

Rear plate portion 11 c is provided as an outermost layer of heat exchange portion 11 on a side opposite to front plate portion 11 a with respect to the plurality of heat transfer plates 11 b. Rear plate portion 11 c is brazed to a rear surface of heat transfer plate 11 b arranged rearmost among the plurality of heat transfer plates 11 b. Rear plate portion 11 c is greater in thickness than heat transfer plate 11 b. Rear plate portion 11 c can thus reinforce heat transfer plate 11 b.

Referring to FIGS. 5 and 6, the plurality of heat transfer plates 11 b are layered on one another. The plurality of heat transfer plates 11 b are arranged as being superimposed on one another in a direction in which front plate portion 11 a and rear plate portion 11 c are opposed to each other.

Front plate portion 11 a is joined to heat transfer plate 11 b arranged at one end (a first end) in the direction of layering of the plurality of heat transfer plates 11 b and rear plate portion 11 c is joined to heat transfer plate 11 b arranged at the other end (a second end) in the direction of layering of the plurality of heat transfer plates 11 b.

Adjacent heat transfer plates 11 b of the plurality of heat transfer plates 11 b are brazed to each other. A gap between a pair of adjacent heat transfer plates 11 b of the plurality of heat transfer plates 11 b defines a flow path through which water and/or hot water passes.

A space between the pair of adjacent heat transfer plates 11 b of the plurality of heat transfer plates 11 b defines a flow path through which combustion gas flows. Each of a space between a pair of heat transfer plates 11 b and front plate portion 11 a and a space between a pair of heat transfer plates 11 b and rear plate portion 11 c also defines a flow path through which combustion gas passes. Heat can thus be exchanged between water and/or hot water which passes through latent heat recovery heat exchanger (secondary heat exchanger) 10 and combustion gas.

Heat transfer plate 11 b has, for example, a substantially rectangular outer geometry in a plan view. Heat transfer plate 11 b is formed, for example, by pressing one flat plate. Heat transfer plate 11 b has flow path projections and recesses formed in pressing. The flow path projections and recesses of heat transfer plate 11 b have a plurality of flow path projections and a plurality of flow path recesses. As the plurality of heat transfer plates 11 b are layered on one another, the plurality of flow path projections and the plurality of flow path recesses define flow paths for passage of water and/or hot water between a pair of heat transfer plates 11 b, and a space between the pair of heat transfer plates 11 b defines a flow path for passage of combustion gas.

A pair of pipe joint portions 14 is attached to front plate portion 11 a. Pipe joint portion 14 is configured to allow water and/or hot water to flow in and out of the plurality of heat transfer plates 11 b. Uppermost heat transfer plate 11 b is connected to the pair of pipe joint portions 14 with front plate portion 11 a being interposed. Each of the pair of pipe joint portions 14 is a pipe joint for connecting a pipe. A flow path in each of the pair of pipe joint portions 14 is connected to an internal flow path of each of the plurality of heat transfer plates 11 b.

A pipe connected to one of the pair of pipe joint portions 14 is a pipe for allowing water and/or hot water to flow into an internal flow path in each of a pair of heat transfer plates 11 b. A pipe connected to the other of the pair of pipe joint portions 14 is a pipe for allowing water and/or hot water to flow out of the internal flow path in each of the pair of heat transfer plates 11 b.

A through hole is provided in each of the plurality of heat transfer plates 11 b. Each through hole communicates with an internal flow path in the pair of heat transfer plates 11 b. The through hole is arranged directly under pipe joint portion 14. The through hole communicates with a flow path in pipe joint portion 14. Therefore, water and/or hot water introduced from pipe joint portion 14 on the water entry side flows through the internal flow path in each of the pair of heat transfer plates 11 b and thereafter exits from pipe joint portion 14 on the hot water exit side.

Case 12 accommodates a plurality of heat transfer plates 11 b of heat exchange portion 11. Front plate portion 11 a of heat exchange portion 11 forms a part of case 12. Front plate portion 11 a and case 12 form a frame which opens upward and downward. Combustion gas is fed through an upper opening and exhausted through a lower opening. Front plate portion 11 a and case 12 surround the plurality of heat transfer plates 11 b.

Case 12 includes a rear wall portion 12 a and a pair of sidewall portions 12 b. Rear wall portion 12 a is arranged to sandwich the plurality of heat transfer plates 11 b between rear wall portion 12 a and front plate portion 11 a. Rear wall portion 12 a is arranged opposite to front plate portion 11 a with the plurality of heat transfer plates 11 b lying therebetween. The pair of sidewall portions 12 b extends from opposing ends of rear wall portion 12 a toward front plate portion 11 a. The pair of sidewall portions 12 b is joined to front plate portion 11 a.

Opposing ends of front plate portion 11 a are bent in a direction intersecting a surface (a main surface) of front plate portion 11 a. The opposing ends of front plate portion 11 a are preferably bent at a right angle with respect to the surface (main surface) of front plate portion 11 a. The opposing ends of front plate portion 11 a extend along inner surfaces of the pair of sidewall portions 12 b. Outer surfaces of the opposing ends of front plate portion 11 a are joined to the inner surfaces of the pair of sidewall portions 12 b. Specifically, the outer surfaces of the opposing ends of front plate portion 11 a are welded to inner surfaces of front ends of the pair of sidewall portions 12 b. Since the opposing ends of front plate portion 11 a extend along the inner surfaces of the pair of sidewall portions 12 b, the opposing ends of front plate portion 11 a are readily welded to the inner surfaces of the pair of sidewall portions 12 b.

Referring to FIGS. 4 and 7, flange member 13 is arranged in an upper end portion 12 c of case 12. Flange member 13 is in a surrounding shape. Flange member 13 includes an extension portion 13 a, an opening 13 b, and a rising coupling portion 13 c. Extension portion 13 a extends from upper end portion 12 c of case 12 to the outside of case 12. Opening 13 b is provided on an inner side of extension portion 13 a. Extension portion 13 a is provided to surround opening 13 b.

Extension portion 13 a includes a first stepped portion and a second stepped portion arranged on an outer side of the first stepped portion. The first stepped portion is arranged on a side of opening 13 b. The second stepped portion is arranged opposite to opening 13 b with respect to the first stepped portion. The second stepped portion is arranged above the first stepped portion. Rising coupling portion 13 c is constructed to rise upward from extension portion 13 a along opening 13 b. Upper end portion 12 c of case 12 is inserted in opening 13 b. Rising coupling portion 13 c is joined from the outer side to upper end portion 12 c of case 12 inserted in opening 13 b. Specifically, rising coupling portion 13 c is welded to upper end portion 12 c of case 12.

Rising coupling portion 13 c includes a peripheral wall portion 13 c 1 and a first cut portion 13 c 2. Peripheral wall portion 13 c 1 is provided to surround opening 13 b. First cut portion 13 c 2 is provided in an upper edge of peripheral wall portion 13 c 1. Therefore, rising coupling portion 13 c is low in height in first cut portion 13 c 2. Case 12 includes a second cut portion 12 d provided in an upper edge of upper end portion 12 c of case 12. Therefore, upper end portion 12 c of case 12 is low in height in second cut portion 12 d. First cut portion 13 c 2 is arranged to be superimposed on second cut portion 12 d. First cut portion 13 c 2 and second cut portion 12 d are arranged to communicate with each other.

Opening 13 b is quadrangular when flange member 13 is viewed from above. First cut portion 13 c 2 and second cut portion 12 d are provided in each of four corners of opening 13 b.

Referring to FIG. 8, a plurality of fins 25 are accommodated in case 21 of sensible heat recovery heat exchanger 20. The plurality of fins 25 are arranged as being layered on and spaced apart from one another. A through hole 25 a is provided in each of the plurality of fins 25. Through holes 25 a are arranged as being superimposed on one another in a direction of layering of the plurality of fins 25. Heat transfer tube 23 is inserted in through holes 25 a in the plurality of fins 25. A water entry portion 23 a of heat transfer tube 23 is arranged in a lower right portion of case 21 in FIG. 8.

Any one of first cut portion 13 c 2 and second cut portion 12 d provided in each of four corners of opening 13 b of flange member 13 shown in FIG. 7 is arranged directly under water entry portion 23 a of heat transfer tube 23 shown in FIG. 8.

As shown in FIG. 8, in sensible heat recovery heat exchanger 20, when a temperature of water and/or hot water which enters heat transfer tube 23 is low or when an amount of heating by combustion apparatus 30 is small, drainage water is produced. Drainage water flows into latent heat recovery heat exchanger 10. Sealing member 60 is placed on the second stepped portion of extension portion 13 a of flange member 13.

Referring to FIG. 9, drainage water which flows into latent heat recovery heat exchanger 10 from sensible heat recovery heat exchanger 20 stays on an upper surface of flange member 13. Since first cut portion 13 c 2 and second cut portion 12 d are provided, drainage water flows down to the inside of case 12 through first cut portion 13 c 2 and second cut portion 12 d.

Functions and effects of the present embodiment will now be described in comparison with a comparative example.

Comparative Example 1 will initially be described with reference to FIGS. 10 and 11. In latent heat recovery heat exchanger 10 in Comparative Example 1, case 12 which accommodates heat exchange portion 11 is configured to be divided into a front member 121 and a rear member 122. Front member 121 and rear member 122 are fixed to each other by a not-shown screw at a boundary between front member 121 and rear member 122. In latent heat recovery heat exchanger 10 in Comparative Example 1, heat exchange portion 11 and case 12 are separate from each other. Therefore, front plate portion 11 a of heat exchange portion 11 and front member 121 of case 12 are each provided. The number of members thus increases.

Furthermore, a not-shown sealing member such as a gasket is required for sealing a gap at the boundary between front member 121 and rear member 122 of case 12.

In latent heat recovery heat exchanger 10 in Comparative Example 1, a not-shown pipe joint portion is attached to front member 121 of case 12 instead of front plate portion 11 a of heat exchange portion 11. Specifically, pipe 11 d for allowing water and/or hot water to flow in and out is connected to heat transfer plate 11 b. Pipe 11 d is inserted in a through hole 121 a provided in front member 121 of case 12. Pipe 11 d is inserted also in the pipe joint portion. Namely, the pipe joint portion is attached to front member 121 of case 12 while pipe 11 d is inserted therein. Therefore, a not-shown sealing member such as a gasket is required for sealing a gap between the pipe joint portion and front member 121 of case 12.

In succession, Comparative Example 2 will be described with reference to FIGS. 12 and 13. In latent heat recovery heat exchanger 10 in Comparative Example 2, first cut portion 13 c 2 and second cut portion 12 d in the present embodiment are not provided. Therefore, drainage water which has flowed into latent heat recovery heat exchanger 10 from sensible heat recovery heat exchanger 20 stays on the upper surface of flange member 13. Since drainage water stays up to the upper edge of rising coupling portion 13 c of flange member 13, a water surface of drainage water is high. Therefore, drainage water may leak to the outside of latent heat recovery heat exchanger 10 over the outer side of flange member 13.

According to latent heat recovery heat exchanger 10 in the present embodiment in comparison with Comparative Example 1, as shown in FIG. 5, front plate portion 11 a of heat exchange portion 11 forms a part of case 12. Therefore, front plate portion 11 a of heat exchange portion 11 can serve also as case 12. Therefore, the number of members can be reduced.

According to latent heat recovery heat exchanger 10 in the present embodiment, pipe joint portion 14 is attached to front plate portion 11 a. Therefore, no sealing member such as a gasket is required for sealing a gap between pipe joint portion 14 and front plate portion 11 a. Since no sealing member such as a gasket is required for sealing a gap between pipe joint portion 14 and front plate portion 11 a, there is no possibility of leakage of heating gas (combustion gas) through the gap between pipe joint portion 14 and front plate portion 11 a to the outside of latent heat recovery heat exchanger 10 due to poor sealing. Therefore, sealability can be improved.

According to latent heat recovery heat exchanger 10 in the present embodiment, a pair of sidewall portions 12 b which extends from opposing ends of rear wall portion 12 a arranged to sandwich the plurality of heat transfer plates 11 b between rear wall portion 12 a and front plate portion 11 a toward front plate portion 11 a is joined to front plate portion 11 a. Therefore, no sealing member such as a gasket is required for sealing a gap between front plate portion 11 a and the pair of sidewall portions 12 b. Since no sealing member such as a gasket is required for sealing a gap between front plate portion 11 a and the pair of sidewall portions 12 b, there is no possibility of leakage of heating gas (combustion gas) through the gap between front plate portion 11 a and the pair of sidewall portions 12 b to the outside of latent heat recovery heat exchanger 10 due to poor sealing. Since no sealing member such as a gasket is required for sealing a gap between front plate portion 11 a and the pair of sidewall portions 12 b, no operation for attaching the sealing member is required. Therefore, assembly of latent heat recovery heat exchanger 10 is facilitated.

According to latent heat recovery heat exchanger 10 in the present embodiment, as shown in FIG. 3, extension portion 13 a which extends from upper end portion 12 c of case 12 to the outside of case 12 is provided to surround opening 13 b. Therefore, sealing member 60 can be placed on extension portion 13 a to surround opening 13 b. Sealing as surrounding opening 13 b can thus be achieved.

According to latent heat recovery heat exchanger 10 in the present embodiment, as shown in FIGS. 4 and 5, rising coupling portion 13 c of flange member 13 is joined from an outer side to upper end portion 12 c of case 12 inserted in opening 13 b. Therefore, rising coupling portion 13 c can readily be welded to upper end portion 12 c of case 12.

According to latent heat recovery heat exchanger 10 in the present embodiment in comparison with Comparative Example 2, as shown in FIGS. 7 and 9, first cut portion 13 c 2 provided in the upper edge of peripheral wall portion 13 c 1 of rising coupling portion 13 c is arranged to be superimposed on second cut portion 12 d provided in the upper edge of upper end portion 12 c of case 12. Therefore, drainage water can flow to opening 13 b through first cut portion 13 c 2 and second cut portion 12 d. Drainage water can thus readily be discharged.

According to latent heat recovery heat exchanger 10 in the present embodiment, as shown in FIGS. 4 and 5, first cut portion 13 c 2 and second cut portion 12 d are provided in each of four corners of opening 13 b. Therefore, first cut portion 13 c 2 can be made by cutting and erecting four corners of opening 13 b in flange member 13. Therefore, first cut portion 13 c 2 can readily be made.

Since hot water apparatus 100 in the present embodiment includes combustion apparatus 30, sensible heat recovery heat exchanger 20, and latent heat recovery heat exchanger 10 as shown in FIG. 1, a hot water apparatus which can achieve a reduced number of members of a heat exchanger can be provided.

According to hot water apparatus 100 in the present embodiment, as shown in FIG. 8, first cut portion 13 c 2 and second cut portion 12 d are arranged directly under the water entry portion of heat transfer tube 23. Since first cut portion 13 c 2 and second cut portion 12 d can thus be arranged directly under the water entry portion where drainage water is likely, drainage water can efficiently be discharged.

A construction in which first cut portion 13 c 2 and second cut portion 12 d are provided in a portion other than four corners of opening 13 b in flange member 13 as a modification of the present embodiment will be described with reference to FIG. 14.

In the modification of the present embodiment, first cut portion 13 c 2 and second cut portion 12 d are provided in a portion between corners of opening 13 b in flange member 13. Namely, first cut portion 13 c 2 and second cut portion 12 d are provided in a side between corners of opening 13 b in flange member 13. At least one first cut portion 13 c 2 and at least one second cut portion 12 d should only be provided. Namely, a single first cut portion 13 c 2 or a plurality of first cut portions 13 c 2 and a single second cut portion 12 d or a plurality of second cut portions 12 d may be provided.

Since the modification of the present embodiment is otherwise similar in features to the present embodiment, the same elements have the same reference numerals allotted and description thereof will not be repeated.

According to the modification of the present embodiment, first cut portion 13 c 2 and second cut portion 12 d can be arranged at any position other than four corners of opening 13 b in flange member 13. Thus, drainage water can be discharged from a portion other than four corners of opening 13 b in flange member 13.

A construction in which first cut portion 13 c 2 and second cut portion 12 d are provided in each of four corners of opening 13 b in flange member 13 is described in the present embodiment and a construction in which first cut portion 13 c 2 and second cut portion 12 d are provided in a portion other than four corners of opening 13 b in flange member 13 is described in the modification of the present embodiment. Arrangement of first cut portion 13 c 2 and second cut portion 12 d, however, is not limited as such. First cut portion 13 c 2 and second cut portion 12 d may be provided also in a portion other than four corners, in addition to each of four corners of opening 13 b in flange member 13.

In the present embodiment and the modification, heat exchange portion 11 may be configured to exchange heat by flow of water and/or hot water between front plate portion 11 a and the front surface of heat transfer plate 11 b arranged in the forefront.

It should be understood that the embodiment disclosed herein is illustrative and non-restrictive in every respect. The scope of the present invention is defined by the terms of the claims rather than the description above and is intended to include any modifications within the scope and meaning equivalent to the terms of the claims.

REFERENCE SIGNS LIST

10 latent heat recovery heat exchanger; 11 heat exchange portion; 11 a front plate portion; 11 b heat transfer plate; 11 c rear plate portion; 12 case; 12 a rear wall portion; 12 b sidewall portion; 12 c upper end portion; 12 d second cut portion; 13 flange member; 13 a extension portion; 13 b opening; 13 c rising coupling portion; 13 c 1 peripheral wall portion; 13 c 2 first cut portion; 14 pipe joint portion; 20 sensible heat recovery heat exchanger; 22 header; 23 heat transfer tube; 30 combustion apparatus; 31 chamber; 32 fan assembly; 33 duct; 34 venturi; 35 orifice; 36 gas valve; 40 pipe; 41 bypass pipe; 42 three-way valve; 43 liquid to liquid heat exchanger; 44 hydronic pipe; 50 housing; 60 sealing member; 100 hot water apparatus 

1. A heat exchanger comprising: a heat exchange portion including a plurality of heat transfer plates layered on one another; and a case which accommodates the plurality of heat transfer plates of the heat exchange portion, the heat exchange portion including a front plate portion provided as an outermost layer of the heat exchange portion, and the front plate portion of the heat exchange portion forming a part of the case.
 2. The heat exchanger according to claim 1, the heat exchanger further comprising a pipe joint portion attached to the front plate portion, the pipe joint portion being configured to allow water and/or hot water to flow in and out of the plurality of heat transfer plates.
 3. The heat exchanger according to claim 1, wherein the case includes a rear wall portion arranged to sandwich the plurality of heat transfer plates between the rear wall portion and the front plate portion and a pair of sidewall portions which extends from opposing ends of the rear wall portion toward the front plate portion, and the pair of sidewall portions is joined to the front plate portion.
 4. The heat exchanger according to claim 1, the heat exchanger further comprising a flange member arranged at an upper end portion of the case, wherein the flange member includes an extension portion which extends from the upper end portion to outside of the case and an opening provided on an inner side of the extension portion, and the extension portion is provided to surround the opening.
 5. The heat exchanger according to claim 4, wherein the flange member includes a rising coupling portion which rises upward from the extension portion along the opening, the upper end portion of the case is inserted in the opening, and the rising coupling portion is joined from an outer side to the upper end portion of the case inserted in the opening.
 6. The heat exchanger according to claim 5, wherein the rising coupling portion includes a peripheral wall portion which surrounds the opening and a first cut portion provided in an upper edge of the peripheral wall portion, the case includes a second cut portion provided in an upper edge of the upper end portion of the case, and the first cut portion is arranged to be superimposed on the second cut portion.
 7. The heat exchanger according to claim 6, wherein the opening is quadrangular when the flange member is viewed from above, and the first cut portion and the second cut portion are provided in each of four corners of the opening.
 8. A hot water apparatus comprising: a combustion apparatus which generates heating gas; a sensible heat recovery heat exchanger which recovers sensible heat of heating gas generated by the combustion apparatus; and the heat exchanger according to claim 1 as a latent heat recovery heat exchanger which recovers latent heat of heating gas.
 9. A hot water apparatus comprising: a combustion apparatus which generates heating gas; a sensible heat recovery heat exchanger which recovers sensible heat of heating gas generated by the combustion apparatus; and the heat exchanger according to claim 7 as a latent heat recovery heat exchanger which recovers latent heat of heating gas, the sensible heat recovery heat exchanger including a heat transfer tube for flow of water and/or hot water, the heat transfer tube including a water entry portion for entry of water and/or hot water in the heat transfer tube, and any one of the first cut portion and the second cut portion provided in each of four corners of the opening being arranged directly under the water entry portion. 